For me until Prometheus' first trailer came out, despite being a massive fan of Alien and Predator, and even liking AVP 2004 in places- I didn't know AVPR even existed until I caught the unrated version in a bargain bin in 2011/12, even then being only 14 I felt a sense that this thing probably did not make waves for a reason.
So in a way, to my childhood- regardless of popular opinion, Alien's always meant three solid films, and one really weird one, while Predator's meant one, but not the one you think- because to child me, Predator's an exhausting film, it takes it's time purposefully, and because I knew Terminator from an even earlier age- I never saw Dutch, I only saw Arnold, so I was always conscious I was watching the star when he was on screen, that I did not like for some reason. I still liked it, but it was Predator 2 that was always THE Predator flick to me, it set my imagination on fire.
Despite my first experience with the Alien films being the BBC's broadcast of Aliens, I still remember the fact I barely watched the film at all, wasn't allowed to but I saw bits without the monsters, the ads between "Burke it was Burke..." and now every-time I get to that part on Blu-ray I expect the ads twenty years on. Then and now, I still like Alien and Alien 3 most, my favourite bit in Alien was the Space Jockey, but I loved basically everything about 3, from the fact I couldn't figure out why the film seemed to change every-time I watched it (Didn't understand the difference between Theatrical and Special Edition), to the atmosphere being the thickest I can even think of in a film to this day, to the frenetic pace of it when the Alien's around, it was and remains my favourite from start to finish. While I always thought there was lulls in Alien and Aliens, even though they're clearly "better" from the script standpoint, and many others. I've always had a soft spot for the more messy, broken, unappreciated things in life.
Oh, and it's got the best soundtrack in the franchise bar none. Covenant comes close tho.
"Let me get this straight, you think Alien Cubed's the best soundtrack in the series?" 
Otherwise I agree with NA, oh and I ADORE Noomi Rapace, she deserved better, but I still prefer Covenant over Prometheus by a mile and a half, and it's got f**k all to do with "genre expectations" it's because I can enjoy Covenant where it succeeds as this over dramatic little intimate Gothic horror picture, while Prometheus has bigger aspirations it also falls on it's face harder and squanders a ridiculous amount of potential.
